interdigitation

Interdigitation is the arrangement of two structures where projections extend between each other, producing an interlocked, finger-like interface. The term derives from Latin inter, between, and digitus, finger.

In biology and anatomy, interdigitation often refers to the interlocking between tissue layers at a boundary. A well-known example is the epidermis and dermis in hairy skin, where epidermal ridges and dermal papillae form interdigitating patterns that increase surface area and mechanical adhesion. Similar interdigitations occur at other epithelial-stromal interfaces and at the boundaries between different tissues.

In engineering and materials science, interdigitated structures are used to maximize contact area while minimizing footprint. Interdigitated electrodes consist of two comb-like electrodes with alternating fingers that interlock. This geometry is common in sensors, microelectromechanical systems, and energy devices, where it improves signal strength or charge transfer.

In geology and mineralogy, interdigitation describes interlocking textures where mineral grains or layering pass into one another, or where different rock facies are juxtaposed with interlocking margins. In botany and zoology, interdigitation may describe interlocking processes in tissues or in morphological features.